Effect of temperature on mechanical behavior of AZ31 magnesium alloy

Strain rate sensitivity and tension/compression asymmetry of AZ31 magnesium alloy at different temperatures and strainrates were investigated.Both of mechanical behaviors are temperature dependent.Strain rate sensitivity increases with increasingtemperature.Thermally activated slip is the source of strain rate sensitivity.At the temperature below or near 373 K,strain ratesensitivity is very little.Tension/compression asymmetry in yielding decreases with increasing temperature.Twinning is the reasonof tension/compression asymmetry.At the temperature above or near 573 K,the material shows little tension/compressionasymmetry of the flow stress.     

聚苯胺的合成、表征及气敏性能研究

用化学氧化聚合法,以苯胺(An)为单体,过硫酸铵(APS)为氧化剂,控制反应温度,在酸性介质(无机酸和有机酸)中合成聚苯胺(PAn)。用傅里叶红外光谱(FTIR)和紫外可见光光谱(UV-Vis)对聚苯胺掺杂前后结构的变化进行了测试,讨论了酸掺杂对聚合产物结构的影响。结果表明电子的离域使聚苯胺主链结构经质子酸掺杂后形成了共轭结构。常温下,通过聚苯胺的气敏性能测试,得知有机酸掺杂的聚苯胺的气敏性能更好,其中用磺基水杨酸掺杂的聚苯胺对1000ppm氨气的灵敏度最高,达到了14.8580,具有实际应用价值。     

东河储层损害机理分析

钻井液和酸化体系与储层流体不配伍是造成油层损害的主要原因。东河砂岩含有不同类型敏感性矿物,利用常规钻井液和酸化技术难以达到保护储层的目的。本文在分析东河储层敏感性损害机理前提下,提出保护油层的2项措施。     

PH敏感性水凝胶的分子热力学模型

本工作是在非离子凝胶的分子热力学模型基础，引入Ｄｏｎｎａｎ平衡项和大分子离子链的静电排斥项对凝胶自由能的贡献，建立了一个新的离子凝胶的分子热力学模型。该模型在解释离子凝胶的ＰＨ敏感性及其各种影响因素，以及预测ＰＨ溶胀曲线方面都取得了较好的效果。     

Platinum particle size effect on the oxidative dehydrogenation of aqueous ethanol

The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m^–3, a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m^–3. A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nm. Hence, the reaction shows a limited structure sensitivity.     

4H-SiC无线无源高温压力传感器设计

高温压力传感器研制的主要目的是解决高温恶劣环境下的压力测量问题,SiC是制造高温压力传感器的理想材料,结合薄膜技术与陶瓷厚膜技术,提出了一种新型的4H-SiC无线无源电容式高温压力传感器设计方案。应用Ansys有限元分析软件进行仿真,600℃时灵敏度为2.65 MHz/bar,说明传感器在高温下具有较高的灵敏度,对制备过程中的关键工艺——SiC深刻蚀进行了验证,刻蚀深度达到124μm,满足传感器制备要求。     

Hydrogen evolution during the oxidation of formaldehyde on Au:: The influence of single crystal structure and Tl-upd

Hydrogen evolution during formaldehyde oxidation in alkaline solution has been monitored by Differential Electrochemical Mass Spectrometry on Au(111) and polycrystalline gold. The current efficiency for hydrogen evolution increases with higher concentration and is in the same range on both, polycrystalline Au and Au(111) electrode. The onset potentials and half-wave potentials are higher on Au(111). Reaction orders for the faradaic current on the bare gold electrodes have been determined as 0.21 for higher and 0.76 for lower concentrations. Reaction orders for hydrogen evolution during formaldehyde oxidation are 1.4 times higher in each case. Tafel slopes in the range of 140-160 mV are found. This signifies that the first reaction step involving the formation of adsorbed hydrogen is largely determining the overall reaction rate. In the presence of thallium adlayers hydrogen evolution from formaldehyde oxidation is largely suppressed. On the thallium modified polycrystalline Au, formaldehyde oxidation is shifted for 100 mV to higher potentials where Tl is partially desorbed and hydroxide is coadsorbed on the modified surface. On thallium modified Au(111), a similar process takes place, but in the same potential region as the onset of formaldehyde oxidation on the bare surface and therefore the formaldehyde oxidation is only slightly shifted. Tafel slopes are decreased to 80 mV/dec in the presence of thallium. In the presence of adsorbed thallium, the first reaction step is in equilibrium, the coverage with adsorbed hydrogen is smaller and its recombination to H₂ is largely suppressed.     

碘溴化银T颗粒乳剂中碘的加入

高感光度乳剂制备中 ,如何利用好碘的掺杂技术 ,对于提高乳剂感光性能起至关重要的作用 ,本文针对碘溴化银T颗粒乳剂中不同的加碘方式、碘的不同分布及不同的加入量 ,对其晶型和感光性能的影响进行了综述。     

Humidity sensitivity of polypyrrole and polypyrrole/SBA‐15 host–guest composite materials

Polypyrrole (PPY) and PPY/SBA‐15 host–guest composite materials have been prepared using chemical synthesis route and characterized by XRD, IR, N₂ adsorption–desorption isotherms, and SEM. The humidity sensitive properties (HSP) of this kind of materials have been studied by analyzing the variation curve of impedance as a function of relative humidity. It was found that the PPY/SBA‐15 host–guest composites materials exhibit better HSP than that of the corresponding pure PPY. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3301–3305, 2006     

一种基于优先级表的实时调度方法

针对单处理器实时系统动态调度问题进行了研究,分析任务的到达时间、执行时间、截止时间和空闲时间等任务属性的敏感度和影响度,提出了一种基于优先级表的调度算法PTBM,使相对截止期越小、空闲时间越大的任务优先级越高。对关于实时任务属性敏感度和影响度的结论验证和与传统的EDF、LLF和PTD算法的对比进行仿真实验,仿真结果表明基于优先级表设计的实时调度算法PTBM具有较高的调度成功率。该方法可应用于实时系统的实时任务的动态调度中。